This study will evaluate the maximum safe dose and duration of regadenoson (Lexiscan) that can be given to people who are having a lung transplant. Regadenoson will be given as a continuous IV infusion. All participants in the study will receive a regadenoson infusion beginning in the operating room during the lung transplant procedure. Participants will be assigned a certain dose of regadenoson to be given over a 12 or 24 hour period.